Metadata enabled push-pull model for efficient low-latency video-content distribution over a network

ABSTRACT

Method, system, computer program and computer program product for a metadata enabled push-pull model and method for efficient low-latency video-content distribution over a network. Metadata is used as a vehicle and mechanism to enable intelligent decisions to be made on content distribution system operation. Metadata is data that contains information about the actual content, and in some cases, the metadata may also contain portions of the content or a low-resolution preview of the content. Aspects of the invention are directed toward the distribution of metadata throughout the network in a way that facilitates efficient system operation as well as optionally but advantageously providing set of services such as tracking, reporting, personalization, and the like.

RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priorityto U.S. application Ser. No. 10/090,709 filed Mar. 4, 2002 now U.S. Pat.No. 7,359,955 entitled “Metadata Enabled Push-Pull Model For EfficientLow-Latency Video-Content Distribution Over A Network,” which claims thebenefit of priority under 35 USC §19(e) and/or 35 USC §120 to U.S.Provisional Appln. Ser. No. 60/272,939 filed Mar. 2, 2001 entitled “PushPull Model Making Use of Metadata For Efficient Content Distribution”and to U.S. Provisional Appln. Ser. No. 60/272,944 filed Mar. 2, 2001entitled “Asset Transfer File Format and Extractor/Parser/Installer ForVideo Content Distribution,” each of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates broadly to computer networks and streamingmedia objects delivered over computer networks. Specifically, thepresent invention relates to efficient techniques, using metadataassociated with content, for making copies of content available atvarious locations inside multiple computer networks in order to providebetter quality of service for delivering streaming media objects.

BACKGROUND

Broadband Internet network infrastructure is developing at rates thatexceed even aggressive analysts' predictions. In the consumer marketsector, telecommunications, cable and wireless companies haveaccelerated deployment of broadband capability to the home with xDSL,cable modem or wireless last mile rollouts. In the corporate marketsector, broadband infrastructure is already available for desktopcomputing applications.

Broadband provides a foundation for the use of good quality IP video inInternet applications. Traditionally limited to Intranets or privatenetworks, broadband Internet connectivity is paving the way forvideo-based applications such as Internet advertising with video, richmedia on web pages, video-assisted ecommerce (video catalogs, travel,etc.), event webcasting, personalized information on demand (news,sports, medicine, lectures, movies, and the like), personal videoexchanges, and training and corporate communications.

Compared to the low frame-rate, small sized videos or low-resolutionstraditionally found on the Internet and delivered on narrowbandconnections, advances in compression technologies have made reasonablequality video possible at connection rates of 300 Kbits/sec (Kbps) orhigher. News stories and lectures with very little motion or action canbe sent at lower bit rates of approximately 100 Kbps to 200 Kbps. Videowith a lot of movement, like a fashion show, needs a higher bit rate tocapture the motion and detail of the scene. For a content providerconsidering Internet distribution, 300 Kbps could be consideredacceptable, and 1 to 1.5 Mbps, excellent. Video catalogues,advertisements, and other commerce-related uses of video require thatthe product be presented at the highest quality levels possible.Broadband rates of 1.5 Mbps and higher afford 30 frames per second (fps)video with CD quality audio. Content with a lot of movement, such asauto racing, needs even higher bit rate, as high as 3 to 4 Mbps.

As Broadband connections proliferate, demand for better performance hasfostered an industry focused on speeding up the delivery of Internetcontent. The majority of these solutions have centered on smallerobjects such as text and images. Video data or objects present problemsdue to their data size and the requirement to provide them at aparticular rate related to the real-time or near-real time play orrendering requirement. Due to its sheer size alone, video is one of themost difficult data types to manage on the Internet or other networkenvironment. A five-minute video clip, encoded and compressed at 1.5Mbps is 56 Megabytes in size. This compares to the few kilobyte datasizes for typical web pages. The strict video timing requirements imposeadditional constraints. When a frame or set of frames arrive past theirintended presentation time (for example, at greater than the nominal1/30 second frame interval in the case of a 30 fps video) the consumeror user experiences jerky playback, dropped frames or segments of thevideo, or other defects that detract from the viewability of the videoand render it essentially useless in a commercial setting. Given thesestringent requirements, delivering quality video over broadband is achallenging problem.

While deployment of the broadband infrastructure is an important step inenabling streaming video over the Internet, upgrades to connectivity andbandwidth alone do not assure the delivery of quality video to largeaudiences with minimal start-up latencies. When video is streamed to theend user via the Internet backbone, video quality is often impacted byproblems. When the source of the video is not close enough to the enduser, packet losses can severely compromise video quality. Packet lossesresult from congestion buffering introduced by network switches androuters between the video source and the end user. Current bandwidthcosts (satellite and terrestrial) make it impractical to streamhigh-quality video from a server to the end user on a point-to-pointbasis. When the video being sent is intended to be at least TV orbroadcast quality video, the problems associated with conventionaltechniques are even more severe.

Existing conventional solutions geared towards improving the performanceof accessing web pages containing rich media (typically including staticimages) are increasingly being used to address the problems withstreaming video on the Internet. Currently, there are two classes ofsolutions that have been employed for improving performance of contentdistribution on the Internet: (i) particular content delivery networkarchitectures and operational schemes, and (ii) content caching schemes.

For purposes of comparison, we first address a content delivery schemethat does not provide any sort of distributed content delivery from thecontent source to the content requester. In this type of system andoperation, content such as an audio or video object is stored on asingle object server only. When a user (perhaps one of millions of usersthat may make a request for the same object) makes a request for theobject, the request is routed to the single object server via whateverset of networks, routers, or other network infrastructural componentsmay be interposed between the user's client computer or otherinformation appliance and the content object source server. The contentobject source server then sends the requested content back to therequester. For small-sized non-real-time delivery to a limited number ofdestinations of certain content objects (such as text or smallcompressed static image files) such direct delivery approach mayrepresent viable operation. However, such an approach does not addresssystem or server scalability or loading problems.

For even a generalized content type, direct delivery without any form ofdistributed content caching inherently exhibits two problems. First, forcontent delivery situations of commercial interest, there is simply notenough network bandwidth at the single central content object server toallow the server to receive and/or to respond to the received requests.Second, even if there were sufficient network bandwidth, there may notbe sufficient processing resources within the server to provide therequested content, particularly when the content includes a large volumeof high quality video. Here the limiting processing resources may be theability of the server hardware to serve more than a limited number ofvideo streams concurrently, the limitations of the server to accessattached storage devices that store the content (e.g. video), or anyother local hardware, software, interface, or other structural oroperational limitation of the server.

When the content is video, a third major problem or limitation with suchdirect delivery becomes evident. Contemporary networks are packetswitched and there may typically be a number of routers and switchesbetween the central object server and the requesting user. Routers aretypically provided with buffers for buffering data (usually in the formof packets) received until it can be forwarded to the next node in thenetwork, however these buffers have limited buffering capacity and inthe event that the amount of data received is greater than the amountthat can be forwarded or stored until forwarding is possible, such dataor packets of data may simply be lost or dropped. For typical web pages,this does not represent a severe problem as the page is simply requestedagain. However, for a video stream intended to be viewed continuouslyand in real time, dropping of a packet of video does not provide anyrecovery mechanism. That segment of video simply cannot be viewed andvarious schemes may be provided to substitute for that video segment,such as a static freeze of the last available frame, blanking thescreen, or other conventional but usually unsatisfactory techniques.

In this context it is noted that conventional Internet infrastructure,particularly network routers or the input or output buffers within orassociated with such routers do not provide any mechanism forrecognizing a packet that has a delivery time requirement or forotherwise maintaining data or packet time-base or isochronous delivery.Therefore other mechanisms may be required if this feature is desired orrequired.

One attempt toward reducing some of the problems associated with directdelivery has been an attempt at general content distribution so as toprovide some scalability and to reduce loading problems as compared tothe single central server architecture. One such approach has been acontent delivery network employing an architecture and operationalscheme commonly referred to as Distributed Content Services (DCS). UnderDCS, portions of web pages containing large amounts of content such asimages are replicated (“pushed” or “push-replicated”) onto a number ofedge servers deployed in last-mile service provider locations close tothe edges of the network, for example as shown in FIG. 1. This contentpush is a priori in that the data is sent to all or selected edgeservers before there is any knowledge that the data will be used or not.It represents one type of edge server caching strategy where content iscached independent of any identified need or request for the content.(An edge server based content pull caching model is described elsewherein this specification.)

Although this a priori pushing consumes storage space (such as hard diskdrive storage) at the edge server, and utilizes network bandwidth overthe network between the content original source server (also referred toas the origin server) and the (or each) edge server, these storage andbandwidth burdens are at least acceptable because the typical web pagesthat are handled are small, again in the kilobyte range and do not havestringent delivery time requirements. By comparison, a 1 hour video thatrepresents information at a rate of 4 mega-bits per second (4 Mbps),would require 14,400 Megabits of storage and the corresponding amount ofnetwork bandwidth for each edge server. Thus while a priori pushing maybe acceptable for selected web pages comprised of text and one or a fewstatic images, it consumes a lot of storage at the edge servers and usesa lot of network bandwidth capacity independent of whether the videocontent will ever actually be requested or delivered to a user. Theunused and wasted resources represent an actual monetary and opportunitycost to the provider.

When a user requests the content either explicitly (such as by making aselection from a video play list) or implicitly by accessing such a webpage or link within a web page, or other content incorporating or makingreference to the content, the edge server closer to the user is directedto serve the replicated content to the user. Edge server “closeness” maybe defined in a number of ways, such as geographic proximity, availablebandwidth, anticipated cost, or according to other rules or policies.

By distributing at least frequently requested content throughout thenetwork, this Distributed Content Services (DCS) approach advantageouslyavoids moving large files through the network backbone for suchfrequently used content. Avoiding the backbone can improve performance(since there are fewer hops between a strategically placed edge serverand the requester client) and is a more cost-effective and scalablesolution. Content delivery networks generally use private satelliteand/or terrestrial networks to connect the originating server to theedge servers. This solution has been widely deployed to improve thedelivery of small media types such as static images and streaming audioon web pages. Unfortunately, it does not provide an optimum solution forreal-time delivery or playback of video and does not address theresource availability, reservation, and management issues.

Another technique used for solving the above problem is the CachingApproach. In the caching approach, distribution of the content to thecaching server is delayed until a first request is made, such that whena user first accesses a web page containing particular content (such astext, images, audio, or video), content is served directly (“pushed”)from the origin server and is subsequently received by and cached by acaching server. While this may accurately be referred to as a “push” itmay also be accurately referred to as a “pull” since the delivery ofcontent from the origin server to the remote caching server is initiatedby the caching server as a result of the received request for theparticular content. Where the caching server is an edge server, thecaching edge server may receive the request directly from theclient/user/requester. Where the caching server is not an edge server,the request for the content is indirectly received from the user throughthe edge server and any intervening network infrastructure and/oragents. Caching servers are placed at strategic points in a network(typically an Internet Service Provider or ISP network) that are closerto the end users. (Edge servers represent one possible type of cachingservers; however, caching servers generally need not be at the edges ofthe network.)

On subsequent access of the same pages by the same or differentrequestor/user, the cached content is served directly to the end user,as for example illustrated in FIG. 2. Caching systems consist ofspecialized equipment at the service provider locations that monitor URLrequests for web objects. Serving content from cached server cantypically reduce Internet backbone traffic by about 50% or more thusreducing bandwidth use associated costs. Serving content from a cachecloser to the end user also improves performance for the reasonsoutlined in the first approach.

Unfortunately, for the later approach that relies on a user requestinitiated pull from the caching server (such as a caching edge server)to the origin server and the subsequent push of the content to the userthrough the caching server (such as the caching edge server), there is alatency or delay associated with receipt and delivery of the content.For simple web pages this delay is acceptable even if a second or a fewseconds, but is unacceptable for a continuing stream of real-time videointended for immediate and continuous playback to the user. Such knownconventional approaches have not provided for any type of networkresource reservation or management that would guarantee or even providereasonable assurances that once a certain initial portion of the videocontent had been sent to the requester or to the edge server servicingthe requester, that the remainder of the video content stream could besent without dropped packets or perceptible delays in the receipt. Wheresuch timely receipt could not be assured, then it would be necessary toincrease the portion sent to the caching edge server prior to initiatingtransmission to the requesting user or to send the entire video prior tobeginning transmission to the requester so that uninterrupted real timeplayback may be accomplished. This would of course result in muchgreater, and perhaps unacceptable, delay in receipt by the requestinguser.

Another problem associated with this model is a content locationproblem. Each edge server that receives a request from a user knows thatit can get the requested content from the central origin server(assuming that the origin server has the content) so that each edgeserver requests the content from that origin server. Under thisoperating model, the edge servers have no information as to which otherof the edge servers may have already obtained the content and thereforerepresent an alternative and perhaps better (lower latency,higher-bandwidth, fewer hops, or the like) or lower cost alternativesource.

Furthermore, as the content is only sent to the edge server if and whena request has been made, there is the likelihood of contention either atthe origin server or on the network to receive the requested contentunder certain scenarios. For example, at prime time viewing hours, theremay be too many requests for a popular new video movie so thatunacceptable delays are encountered or so that the video stream isdisrupted after playback has begun. There may be similar problems withvideo associated with a breaking news story or otherwise when some eventtriggers high interest. This problem is not necessarily encountered forthe a priori push model described herein elsewhere as the content pushcan be scheduled when demands for the content may be low and excessbandwidth is available on the network, such as in the middle of thenight in the time zone of the local market.

Another problem with both of these approaches (Distributed ContentServices or Caching) is that neither of these approaches by itself lendsitself to other business decisions that must or at least should be madeprior to serving the request to the end user. For example, if a user'srequest is directed to his or her edge server directly (which is thecase with majority of the systems and methods in use today), there is noinformation available at the edge to indicate whether the user hasrightful access to the object. Additionally, such systems and methods donot easily lend themselves to keeping statistics on usage patterns,reporting, or the like.

One of the benefits of the Internet or computer networks is its abilityto provide “narrowcasting”—for example, ability to address small groupsof users (and single users) in a targeted manner. The promise ofnarrowcasting is in its ability to provide targeted information to anend user. In the broadcast world (for example, network television), allusers tuned to a particular program (for example, the NBA finals)receive the same program, including the same advertisements. In anarrowcasting world, it should be possible for a user in Cincinnati,interested in automobiles to be seeing advertisements from cardealerships in their local area. This would mean that the informationabout user (“metadata” or “MD”) 108 be available at edge server 110 fordynamic content insertion.

In light of these and other considerations, it will be apparent to thoseworkers having ordinary skill in the art that the current systems andmethods for content delivery and caching are not optimal for thedelivery of certain types of content and especially for high-qualityvideo content such as broadcast quality content. Current contentdelivery networks ensure guaranteed response times by storing all of theresponse-time sensitive data at the edges of the network. Users ensureresponse times by paying for storage costs. The main assumption here isthat storage costs are significantly lower than bandwidth costsassociated with transporting data over the backbone. The sheer sizes ofhigh-quality, full-frame rate video on broadband networks require areexamination of the storage vs. bandwidth issue. To illustrate thisissue, consider two exemplary emerging applications of broadband videoon the Internet: Internet advertising with video content and thedelivery of personalized information on demand.

The Internet ad serving businesses have begun to retool to supportbroadband video in recognition of the potential advantages forvideo-based ads over traditional text-based and/or static image basedbanner ads. For video-based ads, quality, both in terms of the size ofthe video window as well as frame-rates, is very important. Maintaininghigh quality video imagery as well as smooth playback or rendering isimportant relative to a perception of quality of goods and services ofthe advertiser.

The potential storage and bandwidth requirements for such video-basedadvertising are tremendous. Industry sources report that one particularmarket leader in the Internet ad serving business (DoubleClick) servedabout 48 billion impressions in April 2000. Assuming that in a fullydeployed system there would be a million distinct ads and assuming thatthese ads are 30 seconds long video clips digitized at 1.0 Mbps, thenthese ads represent 375 Gigabytes of storage. On 1000 edge servers, thatis 375 terabytes of video data.

With respect to the delivery of personalized information on demand,personalized or customized delivery of information rich in video content(news, sports, entertainment, personal health information, and othertypes of video-rich content.) is a growing application segment on thebroadband Internet. A five-minute video segment at 1.0 Mbps amounts to37.5 megabytes. One such channel of video, which is a 24-hour segmentsplit into 5 minute segments amount to about 10 gigabytes of storage. Ahundred such channels amount to 1 terabyte. Such media stored on 1000edge servers amount to 1 petabyte of storage for one day's worth ofvideo.

For either of these applications as well as for countless others, atleast from a hardware cost perspective, it is impractical to store allof the data inside each of the edge server networks. Additionally, floorspace is at a premium at central offices and cable head-ends where theservers and storage need to be deployed. An intelligent placement ofdata based on measured and anticipated usage is certainly morepractical.

Storage is not about hardware device or disk (or other storage media)storage space alone. An 18-gigabyte disk drive may be large enough tohold approximately two days of one channel at an edge server. However,disk bandwidth rates (or the amount of data that can be read from a diskin one unit of time), limit the number of users receiving data from thedisk simultaneously. To serve more users, the data needs to bereplicated on additional disks, multiplying the amount of space requiredby many times and adding to the storage costs significantly.

There are also content delivery network approach issues. Contentdelivery systems may typically use dynamic replication techniques withinservers in response to increased loading in the networks. Sheer size ofhigh-quality video media makes run-time replication impractical. Loadingusually goes hand-in-hand with increased data traffic in the network.Replication in response to loading congests the networks further. Somecontent delivery networks use satellite transmissions to move data fromdata sources to edge servers connected to receivers. Satellitetransmission is cost-effective if data from a source is broadcast to anumber of receivers simultaneously. Live event webcasting therefore isnaturally suited to this mode of transmission. Due to storage sizerequirements outlined above, applications that require on-demandstreaming from stored data, where data is not uniformly stored at theedges, cannot be deployed cost-effectively using satellite transport.

With advances in optical networking technologies such as DenseWavelength Division Multiplexing (DWDM) that add more channels to eachfiber of an optic fiber network, terabit backbone capacity is likelymoving toward practical implementation and bandwidth costs are likely toget significantly cheaper. However, due at least in part to theisochronous nature of video data, and the number of hops that video datais likely to encounter between a source server and a user computer, itmay be impractical to stream video from the source to the user computerdirectly. This and scalability reasons ensure that edge serving islikely to remain a favored operational and architectural model.

For the various caching approaches, several issues still remain.Networks that use pure caching solutions also suffer from problems dueto the sheer size of the objects they are required to cache. For anyreasonable size cache, the number of objects that can be cached isfairly small leading to high cache chum and low hit rates. Caching ofmedia reduces the level of control that the content owner (or contentdistributor) has over their video objects. The loss of control impliestracking and copyright issues that directly impact revenue generation.The loss of tracking ability also reduces the ability to create revenuevia targeted advertisement. Finally, as networks increase in size,efficiently locating cached media and directing it to the appropriateedge server becomes a challenge.

Thus, there remains a need for an improved and preferably for an optimalsolution for streaming video (or other large time-sensitive data types)over the Internet or other network. The current popular solutions havebeen designed for delivering static images and streaming audio over theInternet and are unable to meet real-time or at least isochronousstreaming video requirements. They also generally fail to provideadequate network resource reservation management for video content.

SUMMARY

Method, system, computer program and computer program product for ametadata enabled push-pull model and method for efficient low-latencyvideo-content distribution over a network are provided. Metadata is usedas a vehicle and mechanism to enable intelligent decisions to be made oncontent distribution system operation. Metadata is data that containsinformation about the actual content, and in some cases, the metadatamay also contain portions of the content or a low-resolution preview ofthe content. Aspects of the invention are directed toward thedistribution of metadata throughout the network in a way thatfacilitates efficient system operation as well as optionally butadvantageously providing a set of services such as tracking, reporting,personalization, and the like.

In one embodiment, the invention provides a metadata enabled server fordistributing a content object to a user over a network in response to auser request, the metadata enabled server including: a computer having aprocessor and a memory coupled to the processor for executing computerprogram instructions, and at least one input/output port for receivingand sending communications from external entities; a storage devicecoupled to the server and storing metadata describing content objectsaccessible to the server including a location from where a contentobject is stored and may be directed to the user; and a controller fordistributing the content object to the user using the metadata andmaintaining isochronous delivery of portions of the content over thenetwork. Method and procedures, system, and computer program fordistributing content and controlling distribution of content are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration in block diagram form of a prior art systememploying an origin server and a network of edge servers.

FIG. 2 is an illustration in block diagram form of a prior art systememploying a network of caching servers.

FIG. 3 is an illustration in block diagram form of an embodiment of thesystem of the present invention as deployed in a global computernetwork.

FIG. 4 is an illustration in block diagram form of an embodiment of anedge server executing computer program instructions to implement theinventive content distribution method.

FIG. 5 is an illustration in block diagram form of the major componentsof a computer as used in conjunction with the system of the presentinvention.

FIG. 6 is a diagrammatic flow chart illustration of an embodiment of aprocedure for delivering video content to a requesting user.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention solves the problems described above by providing amedia content distribution system in which metadata (MD) is used forefficient media content distribution.

The basic tenet of at least some embodiments of the invention describedherein is the use of metadata as a vehicle and mechanism that enablesintelligent decisions to be made on system operation. Metadata containsinformation about the actual content: for example, its physicalproperties, possible locations of the content represented by themetadata, its usage terms, and the like, and others as described ingreater detail elsewhere in this description. In some cases, themetadata may also contain portions of the content (“content prefix”) ora low-resolution preview of the content. Aspects of the invention aredirected toward the distribution of metadata throughout the network in away that facilitates efficient system operation as well as optionallybut advantageously providing a set of services (tracking, reporting,personalization, and the like) that are not present in the conventionalor prior-art systems and methods.

With reference to the illustration in FIG. 3, there is shown in blockdiagram form of an embodiment of system 102 of the present invention asdeployed in a global computer network. Origin server 104 may be a serverof which many types and configurations are known in the art. Typicallysuch servers include a processor, memory coupled to the processor,input/output device, and mass non-volatile storage usually in the formof rotating media hard disk drives, and computer software providingcomputer executable instructions that execute in the processor andmemory to direct the server to operate in a particular manner. In thisembodiment, the origin server 104 includes a metadata database 106 and avideo content (or other arbitrary content) store 108. System 102 alsoincludes at least one and typically a plurality of edge servers (ES)110-n (e.g. 110-1, 110-2, . . . 110-n) each of which also typicallyincludes a metadata database 106 and mass storage 118-n (e.g., 118-1,118-2, . . . , 118-n). The data stored on each edge server mass storagedevice 118-n may usually depend on the particular implementation asdescribed in greater detail herein elsewhere. For example, in oneembodiment edge server storage 118-n will store full video content onceat least a single request has been made for the particular content. Inother embodiments, edge server storage 118-n will store prefix contentsuch as a video prefix content portion. In other embodiments, edgeserver storage 118-n may store both full video content or substantiallyfull video content for a plurality of video titles as well as a prefixportion for some set of video content items. Metadata database 106 andthe content may be stored on the same physical and/or logical device oron different physical or logical mass storage devices. As metadatadatabase 106 is relatively small it may instead or in addition be storedin random access memory, typically with non-volatile backup storage.

With respect to FIG. 4, there is shown in block diagram form anembodiment of a media store including media streaming support 122 forMPEG-1 and MPEG-2 pumps, Kasenna (Mountain View, Calif.) OT 4.0 formatpump, real G2 server, and support for other media service to support avariety of video objects and other content types and formats. Mediamanagement 124 functionality is provided, including functionality foracquisition, storage, and metadata database and data management. Mediadistribution 126 functionality is also provided, including scheduledtransfers, on-demand transfers, and uni-cast and multi-cast operation.Connection manager 116 and storage manager 117 functionality may also beprovided.

With respect to FIG. 5, there is shown in block diagram form the majorcomponents of a computer as may be used in conjunction with the systemof the present invention to receive and render content received. Acommunication connection provides a communication link or path forreceiving content, such as a video content stream, from a server.

By way of a top-level description, in one particular embodiment of theinventive system and method, edge servers or “ES” (that is servers nearthe edge of the network that are primarily responsible for servingcontent to end users) on the content distribution network maintain adirectory that organizes metadata for individual content items typicallyin the form of a universal reference locator (URL) for the item. Thedirectory may be part of a relational database in which functions areprovided that allow easy manipulation of the metadata, or simpler flatfile database structures or lists or tables may be utilized.

In one embodiment, video content URLs, which reference the location ofthe video objects or assets, regardless of the type of media format theyrepresent, are mapped in a homogenous format. User selection ofparticular video content whether by URL or by other designator oridentifier may be recorded in the metadata database, regardless ofwhether the video object is cached or not. Tracking, reporting, billing,targeted advertising, and other data collection and mining operations,are easily enabled using this approach.

In another exemplary application, a web site referenced by a URL mayinclude a server that stores a number of feature length videos (forexample it may store 50 feature length movies), available on demand forusers that pay a fee to receive streaming video that plays the movie.For each movie on the server, there may be provided a correspondingentry or series of entries in the metadata directory that indicate howmany simultaneous plays the host server (such as the origin server or anedge server) can support, how many users are currently viewing copies ofthe movie or other video or content item, how many copies are availablefor viewing, bandwidth requirements, and the like. The metadata ormetadata database (MD) for this server can be stored on the serveritself, as well as exported to other servers in periodic or “on-demand”updates, initiated by the host server or other edge servers in thecontent distribution network.

Metadata can also be used to locate video objects or other contentitems. For example, when a user makes a selection (such as byidentifying a URL) for a video on an edge server (ES), the metadata (MD)corresponding to the selected URL is examined to see if thecorresponding video object is in the cache. If the object is in thecache, the media is streamed directly from the cache. Otherwise,location information in the metadata is used to locate an availableserver that has the video object in its cache. This location can bebased on proximity (number of hops), least traffic load, or otherappropriate manner in which transmission time can be minimized andnetwork resources utilized efficiently. Once the video object is found,it is moved directly from its source to the edge server that requestedit, avoiding percolating the media through cache hierarchies andincurring delays. By employing hint based algorithms for locatingobjects, embodiments of the present invention significantly outperformtraditional multilevel cache hierarchies.

In another aspect, video prefix caching or video prefix contentdistribution (VPCD) may be employed in a manner that involvesdistributing metadata and beginning portions of a video object to edgeservers based on characteristics such as anticipated demand, measuredusage, and type of connection between origin server (OS) 104 and edgeserver (ES) 110. For example, large video prefixes can be used for edgeservers in which greater demand is anticipated, and smaller prefixesstored on other edge servers. If a hit occurs for a video object havinga prefix on the edge server, streaming can begin upon demand, while theremaining portion of the video object is fetched and cached. Typically,origin server 104 will provide video content store (VCS) 108 or othertype of content store, storing the video or other content for all of thecontent items. Each edge server 110 may also provide a video or othercontent store for storing content items, though each edge server'scontent store will typically store only a subset of the content itemsstored in the origin server's content store. (It may be noted thatcertain embodiments of the invention described hereinafter in thecontext of virtualization may not require a content store 108 or willrequire a much smaller one used, that may for example, be used to bufferthe incoming video prior to transmitting it to the requesting user.)

Using Video Prefix Content Distribution (VPCD), initial latenciesinvolved in copying video data from a source server to an edge servercan be practically eliminated. The main principle behind VPCD is thedistribution of metadata and beginning portions (“prefix”) of videocontent to the edges based on characteristics such as anticipateddemand, measured usage and the type of connection between the originserver and the edge server. For example 10, 20 . . . 100% of the videocontent may be replicated (“pushed”) at the edge servers based onanticipated demand and service-level agreements. If a hit occurs for avideo with prefix-content, streaming starts right away, while the restof the content is fetched in parallel (“pipelined”) and cached. Thisreduces the a priori storage space requirements while eliminatinglatencies of initial access. When cache is recycled, portions of contentare retained along with metadata.

In embodiments of the invention that provide for prefix caching orstorage, the video content that is stored in the origin server videocontent store and delivered to the edge servers in response to a requestmay be the full length of the video or the full length of the videominus some initial portion corresponding to the video content prefixportion. As the amount of video content prefix may vary from time totime and from network portion to network portion, it may generally bedesirable to store the full length video content so that an appropriateportion (possibly with overlap) may always be available at any edgeserver to send to any other edge server even though some edge serversmay or may not implement prefix caching and even though those that doimplement prefix caching may cache different amounts or time lengths ofcontent.

When received by a requesting user, the content is rendered or played ona user content rendering or playback device 120, such as a computer,television, set-top box, or other device or system adapted to receivethe content stream (video). Alternatively, the content may be stored forlater playback or rendering.

Having described some top-level features and advantages of elements ofthe inventive system and method, attention is now directed to a moredetailed description of the embodiments of the inventive system, method,computer program and computer program product, and operating model andmethod. It is noted that aspects of this invention apply to a largeclass of content objects, and has particular applicability tomulti-media objects which include video and audio components. Referenceswith this description relative to video, video objects, video content,and other similar terms may be interpreted to mean all forms ofconventional video, movies, cartoons, animations, all forms of timesequenced imagery, and the like, and independent of whether including anaudio component or track or not.

Metadata, the defining data that provides information about ordocumentation of other data managed within an application or environment(or more simply data about other data), is used to identify, describe,locate, fetch, and cache video objects for streaming to users from theedge servers. Various embodiments or sets of metadata may be used inconjunction with different embodiments of the inventive system and theproperties and capabilities desired for the system and method.

For example, the metadata may identify and describe the video object orasset, such as its physical characteristics (formats, size, bit rate, orthe like physical or logical characteristics), and the location orlocations of the actual video objects content on the network from whereit may be accessed, transferred, and/or served. Usually one of thelocations will be the origin server and according to particularembodiments of the invention, one and typically a plurality of edgeservers. (Note that in at least one embodiment of the invention thatincorporates prefix caching, only portions of the entire video may bepresent at certain locations and that in such embodiments the metadatamay also or alternatively identify servers where the prefix portion ofthe full video is stored or cached.)

The metadata may also provide information regarding ownership and/oraccess rights associated with the content, as well as “time-to-live” orexpiration attributes such as may be required when a video object hasbeen purchased for distribution over only a limited defined period oftime, such as when a limited term license has been obtained forcopyrighted material. Rights information may for example provide anindicator identifying either when, where, and/or to whom the content maybe delivered (or when, where, and/or to whom delivery is prohibited).This permission or prohibition may also or alternatively for example beassociated with the geographic or nation state location of the edgeserver, particular domains, be in the form of a list or database, oraccording to other rules or policies. One example, would prohibitparticular sexually explicit video material from being sent to nationstates or countries to which such material is offensive or prohibited.Politically sensitive material may be prohibited from being sent toother regions.

The metadata may also define or specify the “cost” associated withproviding the content from a first (source) location on a network toanother second location on the network, the second location usuallybeing the edge or other server that will serve the content to therequester. Where separate networks are involved, the cost may includethe cost of crossing over from one network to the other. Cost factors,may for example include one or more of tariffs for use of networkbandwidth, cost of storage on particular locations of data storagedevices, requirements to use external entities or avoid use of externalentities, as well as other factors associated with transport and/orstorage. Because the cost associated with content retrieval andtransport from location to location may change according to networkconditions or other factors, an external agent having access to networkconditions, network tariffs, contractual information, current biddingforms, or other facts that would influence cost and suggest alternativelocations and/or network routings may be employed.

Quality of service (QOS) requirements may also be specified in themetadata. QOS information would identify particular levels of content(e.g. video) quality that must be assured for the material to be served,selected for example from frame format or video quality, playback ratedeviations permitted, and other Internet type quality of servicecriteria as are known in the art.

In other embodiments, the metadata may also provide individual framesfrom the video, shorter full resolution segments of the video, lowresolution renditions of the video, or other forms of imagery derivedfrom or relating to the video itself, such as may be useful orentertaining to the user either in enjoying the full video or making aselection to watch the video. The metadata may also provide documentaryinformation, such as textual information about the video. In someinstances such metadata may be rendered to the user during any shortdelay associated with receiving the video or other content once therequest has been made.

In embodiments of the invention providing or supporting content prefixcaching (described in greater detail below), the content prefix (such asvideo prefix) that is an initial smaller portion or subset of the largercontent may be provided as an element or component of the metadata. Inother embodiments, such content prefix may be provided separately.

In at least one embodiment the metadata consists of (i) a globallyunique identifier that identifies and optionally describes the contentassociated with the metadata, and (ii) a location or locations at whichthe content may be found, usually in the form of at least the originserver identifier and more typically also the identities of edge serversthat cache the content. Other metadata elements may optionally butadvantageously be provided to support other desirable contentdistribution features. By way of highlight and summary, these otheroptional metadata elements may be selected in any combination from theset: (iii) cost of retrieving the content from each location; (iv)content format such as MPEG version, RealVideo, or other known or to bedeveloped audio and/or video formats; (v) rights information; (vi)time-to-live or expiration information; (vii) quality-of-service; (viii)content subset or preview derivative; such as single frame video,low-resolution video, limited length video, textual description, or thelike; and/or (ix) content prefix such as defined time duration of actualfull video. The invention further contemplates that the metadata mayinclude any other data or information that describes the content,assists in its localization or routing to a requester, controls accessto the content, assists in maintaining a desired level of quality, orotherwise reduces per server or total storage requirements, or reduceslatency.

The present invention advantageously provides separation of the metadatapath (control plane) from the data path (data plane). System operationincludes two primary aspects: (i) content playback or serving, and (ii)system administration which provides for one or more of loading,creating or adding, updating or modifying, and deleting metadata andcontent. Advantageously, the content and the metadata associated withthe content (or portions of the metadata) may be loaded or updatedseparately. For example, a change in content rights may be made withoutany need for updating the contents itself, the metadata having aglobally unique identifier (or at least unique within the system) thatidentifies it to the content which also provides an identifier in such amanner that the content data and its metadata are identified to eachother.

Metadata is distributed throughout the network and portions of themetadata are stored in servers that receive metadata updates. Sincetypical metadata for any particular video are orders of magnitudesmaller than the video data files themselves, distribution of metadatain the network and storage at the edge servers (or even at clientsdirectly) is a viable operation and does not significantly impact edgeservers storage.

In the event that the system is configured to provide different formatsof the same content, then such format variations may be identified inthe data structure of the metadata database, or where provided in thedata structure of a separate directory server, so that the mostappropriate format may be selected to satisfy the request. The datastructure may be a simple list, a table, a hash, a relational database,or other data structures as are known in the art.

The directory server may typically be a different machine than theorigin server or the edge server, but other embodiments may provide thedirectory on the same machine as the origin or edge servers. One or aplurality of directories or directory servers may be provided accordingto any of these configurations. A plurality of directory servers areadvantageously provided to provide redundancy and reduce loading on anyparticular server during peak loads.

Attention is now directed to an embodiment of a procedure for installingcontent data and metadata associated with the content data on thesystem, network, and/or components thereof. This procedure is describedrelative to the diagrammatic flow chart illustration in FIG. 6. First,it is necessary to install, generate, or otherwise place the content(video) into the system and if not initially installed onto the originserver then install onto the origin server using known techniques.

Next, create the metadata for the content. This metadata creation may bedone at any time including before, during, or after the content (video)is created so long as the content is sufficiently well defined to permitgeneration of the metadata for the content. The metadata at this stagemay include only the globally unique ID and an origin server locationidentifier. The origin server location is identified in the metadataeven though the video may not actually have been installed on the originserver at that time because it will have been installed there by thetime the metadata is actually used or queried. The metadata maysubsequently be modified or updated to reflect changes in contentstorage location.

Supplemental metadata elements may optionally be added as required ordesired to provide optional features, capabilities, and performance. Forexample, the metadata may be augmented with other than a minimum set ofelements to identify rights, format, or other of the characteristics ofthe content as described herein above. This additional metadata mayoptionally be packaged with or attached to the content and extractedfrom the content thereby eliminating any manual or separateupload/download steps. The metadata may alternatively be manuallyentered such as from a text form, uploaded or downloaded from anexternal source, or automatically be extracted from some file, such asthe content data file or any other file. For example, for video contentin the MPEG-7 format, metadata may be included with the file andextracted from it.

A push, and desirably a “scheduled push”, of the metadata to the edgeservers is performed. In one embodiment, the metadata is pushed to alledge servers. In another embodiment, the metadata is pushed to aselected subset of edge servers. Note that the full content (typicallyMegabytes or Gigabytes) is not being pushed to the edge servers, onlythe metadata (typically hundreds or a few thousands of bytes) is beingpushed and represents orders of magnitude less data than the contentitself for most video content of interest here. A scheduled push is apush performed according to a specific schedule or schedule policies andis usually designed to minimize cost and/or disruption to other networkactivity. Conveniently it may be performed during non-peak hours(overnight) and coordinated in time over the system so that the push isnot attempted to all edge servers simultaneously but spread out overtime to reduce peak bandwidth needs and server or other network nodeloading.

Where it is optionally but desired to provide derivative versions of thecontent, such as low resolution and/or short video clips, or to providea content prefix portion, these may also be pushed to the edge serversas part of the metadata or otherwise. Embodiments of particular systems,methods, and computer program for performing prefix caching aredescribed in greater detail below and in co-pending U.S. Utility patentapplication Ser. No. 09/774,204 filed Jan. 29, 2001 and entitled PrefixCaching For Media Objects and assigned to the assignee of the presentinvention, herein incorporated by reference.

In another optional embodiment, when the system and method provides orutilizes one or more servers other than the origin server and the edgeserver, such as one or more directory servers, the content metadata mayalso be pushed to the directory server. This configuration is optionallyprovided as an optimization of the basic system and method and providesa single location data structure that may be queried to identify alllocations at which a content item is located. Directory servers may bereplicated at a plurality of locations throughout the network.

The metadata is then installed on the system. (It is noted that metadatamay be installed and/or updated on the system without reinstalling thevideo or other content.) Once the scheduled push has been performed, themetadata is updated to reflect the additional content and metadatachanges.

After both the content and the metadata have been placed on the system,the system is operational relative to these changes. Until the metadatahas been updated to reflect changes at a particular server, these remotelocations may be unaware of the new content or the locations of the newcontent or both; however, the system remains operational.

It is noted that this hybrid “push” and “pull” with metadata basedmethod and system have many advantages over conventional systems andtechniques. In a conventional pull method, there is no metadata and notracking capability is available as to content. In the system describedhere, metadata data records contain fields to track a variety ofcharacteristics and parameters, for example embodiments of the inventionmay provide for metadata records containing fields to track one or acombination of: the number of users that accessed the content, thenumber of users that were denied access to the content, the frequency ofaccess, the length of viewing, or the like. Such information can then beused for data mining purposes: for example, if the frequency of accessof a particular content goes over a preset threshold, the system cantrigger an operation that eventually results in the “push” of thecontent from an origin server (or any other server) to the rest of theedge servers (or to some sub-set of the rest of the edge servers). Thecollected metadata is sent back to an origin server or any other server,either in real-time or packaged and sent periodically or according toany other desired schedule. This optional tracking capability storesuser access data (possibly individual user data but more typicallystatistical data in the interests of maintaining user privacy) inmetadata records on the edge server, or in any external locationdesignated for gathering, collection, and/or analysis of the user accessdata. Typically, the user access data would be gathered at each of theedge servers, and might include by way of example but not limitation,the number of requestor's for each content item, the time of day thatthe request was made, the delay period between the request and thesatisfaction of the request with playback, the sufficiency or excess ofcontext prefix information, the frequency of user disconnects prior tothe content being delivered, ratings information or information fromwhich ratings information may be derived, frequently requested contentitems, items in the directory that are infrequently requested, and anyother information that may assist in tuning the network configurationand content delivery, selecting content and content formats, orotherwise tuning or optimizing performance. This collected user accessand performance data (a type of metadata in itself) is advantageouslystored and pushed back to a processing location for analysis andreporting. The analysis may include various data mining techniques,statistical analysis, or other tuning and/or optimization techniques.

As a result of the collection, tracking, and analysis a decision may bemade for example to modify the length of the cached content prefix, suchas by shortening or lengthening the prefix. Alternatively or inaddition, a decision may be made to push (push now or scheduled push) anentire content item (such as a complete video) for one or a selectedplurality of content items. This may occur for example, when based oncertain trends in other regions (such as a large number of requests fora particular content item in an eastern time zone region or market) thatthe same content item will be requested in the same time slot in apacific time zone region or market. This type of trend based push may bereferred to as regional push now and would alleviate the need to laterpull a content item into edge servers in that region when for examplebandwidth may be more expensive or not so readily available. Quality ofservice may clearly be maintained at higher levels using this approach.

The key point is that the system and method permit this user and systemperformance data to be collected, mined, and analyzed in a variety ofways and used to modify, tune, and improve or optimize performance andreduce operational costs. Some of these same techniques andinformational elements may also be used for content and deliverypersonalization based on some user characteristic that are either inputinto the system (such as via a user registration or questionnaire) orderived by the system such as time zone of user requester, computer ornetwork access characteristics, prior selection history, networkidentifier, or other parameters derivable from the edge server.

Several embodiments have been described in which the origin serverincludes very large volume storage capability so that all orsubstantially all of the content is at least available on the originserver. These and other embodiments have also provided for content to becached to the edge server after the first request for the particularcontent. In such cases, the edge server also needs to have relativelyhigh storage capacity to handle all of the content download or playbackrequests made by users.

For networks having sufficiently high bandwidth and availabilitycommunication channel links or pipes between the origin server and theedge server, a further embodiment eliminates or substantially eliminateslocal content storage or caching of complete content items (e.g. fullvideos) on the edge servers. Rather, once a user request is made to anedge server, the edge server pulls the requested content from the originserver and initiates playback to the requesting user once a sufficientquantity of the requested content has been received. The network isconfigured in such a manner that resources are available for suchreal-time delivery with some predetermined or specified probability.Optionally, but desirably a initial or prefix portion of each contentitem is cached so that playback to the requesting user can begin withlittle or no delay. The length or playback duration of the prefix may beadjusted according to measured and/or predicted delay associated with acontent request by a particular edge server to a content source such asthe origin server or other content servers or cache servers that may bedistributed in the network.

It will be appreciated that embodiments of the invention are designed tointeroperate in the manner described over existing network and Internetinfrastructure so that such infrastructure need not be modified tosupport the inventive system, method, or computer programs. It will alsobe appreciated that different portions of the existing Internet or worldwide web infrastructure support different data rates, have differentbandwidths, different signal characteristics, and may support differentperformance levels.

Where very high bandwidth and availability network connections areprovided, even the cached prefix may be eliminated, though in otherembodiments a shorter prefix may be stored.

This type of operation may generally be referred to a virtualization ofthe network and storage in part because the high-capacity storageassociated with the source origin server is a sort of virtual storagefor each of the edge servers. It will be appreciated that a singlenetwork may support both local storage at the edge servers wheresufficiently high-bandwidth and high-availability network connectionsare not supported and virtualization where they are available.

It will be appreciated by those workers having ordinary skill in lightof this description that the inventive system and method distribute themetadata to a plurality of locations (e.g., to the origin server andedge servers, or to the origin server, edge servers, and directoryservers: this is the control plane; distribute content to a plurality oflocations, using information embodied in the control plane, but theactual path of the distribution may be different from the data path.Extensive use of metadata separate from the actual content not onlyenables cost-efficient system operation, but also the implementation ofbusiness functions related to the actual use of content. This differsfrom known conventional systems and methods which provide merely asingle non-distributed directory and provide either no metadata ormetadata at only a single location.

An embodiment of the request response and playback procedure 300 is nowdescribed. A user submits an implicit or explicit request (Step 301) fora content item (such as for a video V) to a web site, portal, or othernetwork access point. This user is referred to as the user, userrequester, or simply as the requester. An entity within the networkreceives the request and if this receiving entity is not an edge server,forwards it to an edge server. We assume for purposes of descriptionthat the edge server receives the request directly from the user andignores any other intermediaries, service providers, routers, or thelike that may actually be interposed between the requester and the edgeserver.

The edge server receives the user request for video V (Step 302) anddetermines whether its local directory includes a directory entry forvideo V (Step 304). In one embodiment, the local directory storesentries indicating the availability of the content, the rights to thecontent, and the like. When a user selects a video title displayed onhis computer, TV set via a set-top box, or other information applianceor access method, the user essentially transmits a URL or other globallyunique identification for the video (or other content item) to thenetwork. Intelligence embodied in the network (such as proximity of theuser to an edge server near his/her geographic area) directs the requestto that server. The edge server receiving the request examines itsdirectory to determine if the metadata for the video V is in itsdirectory (Step 304). If the metadata is located, it will indicatewhether the video V is completely stored on the edge server storage,whether video V is currently cached inside the computer's main memory orother storage, or whether video V is only partially available (forexample, the video prefix only). If only the metadata for video V isavailable, it will indicate where in the network copies of video V maybe available (either at video V's origin server or on other edge serversthat have fetched video V and are willing to serve it to our particularedge server). If it is determined that the metadata for video V is notin the receiving edge server's directory, an optional query is made toan external directory or directories for the selected video V (Step312). These external directories may for example be selected from one ormore of edge servers themselves or may be independent directoriescreated for the purpose of making locating the videos easier (such asthe Domain Name Service implementing Internet host name resolutions),among others.

If the metadata information relative to optimal location of video V isin one of the directories, then a source location for the video V isidentified (Step 320) as described in greater detail below. If it is notavailable, then the query fails (Step 316) with optional but desirablenotification to the user.

If it is determined that the video V is in the receiving edge server'sdirectory, a further but optional determination may be made to determineif the requesting user or a group of users having one or morecharacteristics in common with the requesting user should be allowed toaccess the video V (Step 306). This optional test may pertain to theuser having paid an access fee, accessing or not accessing from aparticular geographic region associated with the user's point of entryto the network, rights management in general, or any other rule, policy,criteria, list, event driven or other access or permission basis. If theuser is not permitted access the request fails (Step 307) and the useris desirably informed either that the requested video is not availableor that the user does not have the right permission to receive thevideo. If this optional test (Step 306) is not performed in a particularembodiment then instead, if it is determined by a process executing inthe edge server that the video V is in the receiving edge server'sdirectory, a further determination may be made as to whether the entirevideo V is in the edge server's (my) local cache or storage (Step 308).

If it is in the edge server's local cache then the edge server startsplayback of the requested video V to the requesting user (Step 310).Optionally, though advantageously, the system or component thereof suchas the edge server that will playback the video V will verifyavailability of network resources between the edge server and therequesting user and/or reserve such network resources (Step 309) so thatdelivery or playback to the user may be accomplished according to anyestablished playback minimum requirements of quality of servicerequirements. Embodiments of the inventive system and method may furthermake a determination as to whether a required quality of service (QOS)requirement can be met by the available network resources (and furtheroptionally by the quality and format of the video V itself) and whensuch QOS can be met permitting playback and when such QOS cannot be metnot allowing playback (Step 312). This restriction on playback may forexample, be placed by the owner of the video V, the distributor of V(such as for example an advertiser), so that the intended quality andpresentation effect of the video message may be maintained.

On the other hand, if the determination as to whether video V is in theedge server's cache (Step 308) indicates that it is not in the cache,then an alternative source location for video V is made by querying themetadata stored locally on the edge server (Step 320). Advantageously,this identification of a source location from which to obtain therequested video V is made in an intelligent manner such as bydetermining the optimal source location considering network closeness ofthe video V, cost to move the video V from the possible source locationsto the edge server making the query, and available paths and bandwidthover those paths, and the like factors. The analytical process involvedin the source identification and selection may be performed locally onthe edge server using the stored metadata, or may utilize an externalprocess using the locally stored metadata, or metadata distributed toand stored on that external process server, or within the origin serverusing metadata stored there. In a preferred embodiment, the selection ismade locally within the edge server using current metadata storedtherein and optionally but advantageously using other information ordata indicative of network resource availability and performance andusage costs.

In embodiments of the invention that provide separate directory serverfunctionality, finding the optimal source location for the requestedvideo V may be made utilizing a separate directory server that receivesmetadata updates from the system.

Once a source location (and optionally an “optimum” location given theset of possible locations) for the video V has been identified (Step320) a determination as to whether network resources are available todeliver the video from the identified source server and the requestingedge server is made (Step 322). These resources are then reserved (Step326). If it is determined that adequate resources are not available andcannot be reserved within a predetermined (or otherwise determined)acceptable period of time, either the request fails (Step 324) andnotification of such failure is communicated to the requestor orpreferably, an additional determination is made to identify a new source(Step 320). In practice, the determination as to whether resources areavailable (Step 322) may be part of the step of finding a sourcelocation (Step 320) or a separate step. Advantageously, it is combinedso that identifying the best or optimal source location takes intoaccount the available network resources, and the quality of service ofthe available network resources. In other embodiments, performing thisas a separate or even as an additional check may be desirable wherenetwork resource availability may change rapidly so that the check wouldbe made just prior to initiating a pull of the video V from theidentified source location back to the requesting edge server (Step328).

In yet another alternative embodiment, the step of finding a sourcelocation for the video content may provide for finding a plurality ofsource locations (optionally ranked in order of preference as theprimary source) so that in the event that network resources for thepreferred or optimal source are not available, one or more alternativesources have already been determined, and network resource availabilityfor the alternative source locations can be immediately determined insuccession without repeating the finding step. This may be of particularbenefit under dynamic network conditions.

Once the source location has been identified and network resourceavailability verified, the edge server begins pulling the video Vcontent from the identified source destination (Step 328). Because itwill take some period of time for all of the video to be communicatedfrom the source to the edge server, once the process has begun, adetermination is made as to whether there is a sufficient amount of therequested video V so that playback to the requesting user may beinitiated and maintained according to an acceptable manner. Theacceptability criteria may be established in a variety of ways, but forexample may be set so that there are no discontinuities in playback,maintenance of predetermined playback rate, providing set QOS, orotherwise establish to maintain desired video quality. In general, theamount of video required to have been pulled may depend on the nature,quality, and availability of the network resources between the sendingsource server and the receiving edge server. Typically, a greater amountof received video is required for poorer intervening network resourcesthan for better intervening network resources.

When it is determined that sufficient video content has been received(Step 330) playback may begin to the requesting user from the edgeserver (Step 310). The edge server however, continues to pull orotherwise acquire video content from the identified source until all ofthe video V content has been received and stored local to the edgeserver.

In one embodiment of the invention, the edge server is able to receivedifferent portions of the video V from alternative source locations andassemble them at the edge server for uninterrupted playback to therequesting user. This optional feature, may for example, be utilizedwhen the video V is particularly long and where the source or elementsof the network resources become unavailable during the transmission,such as in the event of a failure. In yet another embodiment, the sourceand network routing may be modified so as to reduce total cost ofdelivering the selected video V to the requester. For example, underthis optional operating procedure, in the event that only an expensiveor slow network path were available at the time the initial transferneeded to begin, but a later cheaper or faster path became available ata later time during the transmission, the source and/or delivery pathmay be dynamically changed to take advantage of changed source serverand/or network resource conditions.

Once the full video V has been received by the edge server, the metadatawithin the edge server is updated to identify that the full video V isnow cached within the edge server (Step 332). Optionally, but desirably,the metadata in other of the edge servers is updated either at the sametime, or as part of a schedule update (Step 324). The changed metadatais also desirably communicated to the origin server for storage there,and to the extent that the origin server is responsible foradministering metadata throughout the system, for subsequentcommunication to and storage by the other edge servers. In embodimentsof the invention that provide a directory server, the modified metadata(or an indication of the particular change in the metadata) iscommunicated to and stored in the directory server.

It will be appreciated that the above procedure has been described forembodiments of the inventive system and method that do not utilize theoptional content prefix caching, for example video prefix caching. Whensuch video prefix caching is provided, each of the edge servers willhave stored an initial playback portion of the video V and can beginplayback at an earlier time and without waiting for a sufficient portionof the video content to be pulled from the source location. In theseembodiments, playback may begin as soon after the video V has beenidentified and without waiting for sufficient video V to be pulled fromthe source. The precise point in time may generally depend upon theamount or length of prefix that is cached in the edge sever and theanticipated time required to locate an available source for the fullvideo, reserve network resources between that identified source, andcommunicate the video V to the destination edge server. In oneembodiment, the objective is to delay playback for only a short time (ifat all) so that before the cached video prefix has been completelyplayed or exhausted, sufficient video will have been received from thesource to support continued interrupted play. Deterministic orstatistical models may be used to tune the system, method, andprocedures to accomplish this objective.

Other embodiments described herein pertain to models in which videocontent is not locally stored at the edge servers, or in which only aprefix portion of the video content is stored in the edge servers, andthe system and method rely on post-request communication over highbandwidth and high-availability network resources. In these embodiments,the above described procedure 300 may be modified such that queries arenot needed relative to the presence of the video V in any particularlocation as the location will be known, but in some situations placing agreater emphasis on identifying network resources to support thevirtualization and access to remote storage over high-capacityconnections.

Having described numerous embodiments of the invention, it may be notedthat much of the description has focused on a particular type ofcontent, that is video content, and more specifically video movies orother video content that is relatively large and for which playbackrequires maintaining a time synchronization or isochronous deliverybetween different segments of the content. It will be noted that this isa different type of content than traditional web pages which are neitherlarge nor require isochronous delivery. The invention is not limitedonly to videos and it will be appreciated that the inventive system andmethod may be applied to other content types existent now or developedin the future for which isochronous playback or delivery and large filesize are issues.

Having disclosed exemplary embodiments and the best mode, modificationsand variations may be made to the disclosed embodiments while remainingwithin the scope of the present invention as defined by the followingclaims.

1. A method for distributing a content object to a user over a networkin response to a user request, said method comprising: storing metadatadescribing content objects in a local storage device accessible to aserver, the local metadata storing including storing at least onelocation from where a particular one of said content object is storedand may be directed to said user; and locally controlling distributionof said content object to said user over said network using said locallystored metadata and maintaining isochronous delivery of portions of saidcontent over said network.
 2. A method as in claim 1, wherein saidlocally controlling includes controlling a request response and playbackprocedure executing as software.
 3. A method as in claim 1, wherein saidnetwork comprises the Internet.
 4. A method as in claim 1, wherein saidnetwork comprises a packet switched communication network not in itselfhaving means for maintaining isochronous delivery of a content itemseparated into a plurality of packets for communication from said serverto said requesting user.
 5. A method as in claim 1, wherein said contentitems are internally accessible to said server.
 6. A method as in claim1, wherein said content items are externally accessible to said server.7. A method as in claim 1, wherein said local storage storing metadatastores data selected from the set of content physical properties,content storage locations, content usage terms, content usage rights,content playback duration, content prefix cache status, content networkrouting cost information, and combinations thereof.
 8. A method as inclaim 1, wherein the metadata also includes a prefix portion of thecontent or a low-resolution preview of the content.
 9. A method as inclaim 1, wherein the locally controlling distribution of said contentobject includes locally performing or controlling performing of arequest response and playback procedure.
 10. A method as in claim 1,wherein said local storage stores at least one content item that isintended to be rendered for presentation at a predetermined time rate.11. A method as in claim 1, wherein said at least one content itemcomprises a video content item having image element frames and audioelements that is intended to be rendered for presentation on a playbackdevice at said predetermined time rate so as to provide substantiallythe same visual and audio rendering to a viewer a when generated.
 12. Amethod as in claim 11, wherein the network comprises a packet switchedInternet network, and the amount of data comprising said video contentitem is greater than the amount of data that is communicated in a packetover a packet switched Internet network.
 13. A method as in claim 1,wherein the amount of data comprising said video content item is anamount of video content that when rendered in real-time at an intendedplayback rate would exceed a fraction of time of broadcast qualityvideo.
 14. A method as in claim 1, wherein the amount of data comprisingsaid video content item is an amount of video content that when renderedin real-time at an intended playback rate would exceed 60 minutes ofbroadcast quality video.
 15. A method as in claim 1, wherein said videocontent item comprises substantially a fill-length feature film in avideo format.
 16. A method as in claim 1, wherein said network comprisesInternet network infrastructure.
 17. A method as in claim 1, whereinsaid network includes a network communication link comprising Internetinfrastructure and Internet communication protocol.
 18. A method as inclaim 1, wherein said metadata is used to enable intelligent decisionsto be made on a content distribution system operation and contentrouting.
 19. A method as in claim 1, wherein said metadata containsinformation about the actual content including its physical properties,possible locations of the content represented by the metadata, its usageterms, and combinations of these.
 20. A method as in claim 1, whereinsaid metadata includes a globally unique identifier describing thecontent object and at least one location at which said content objectmay be found.
 21. A method as in claim 1, wherein said content objectcomprises a video content object having an amount of data requiring aplurality of packets for communication over a packet switched network,and said locally controlling providing isochronous delivery from saididentified content location to a playback device of said requestinguser.
 22. A method as in claim 1, wherein the local storing and thelocal controlling are performed at an edge of the network.
 23. A methodas in claim 1, wherein the local storing and the local controlling areperformed at a different location that the server.
 24. A method fordistributing a content object to a user over a network in response to auser request, said method comprising: an origin server; coupling aplurality of edge servers to an origin server; enabling each said edgeserver to be metadata enabled and adapted to execute a method fordistributing the content object to a user over the network in responseto a user request including: storing metadata describing content objectsin a local storage device accessible to a server, the local metadatastoring including storing at least one location from where a particularone of said content object is stored and may be directed to said user;and locally controlling distribution of said content object to said userover said network using said locally stored metadata and maintainingisochronous delivery of portions of said content over said network.